^ abcdPegasus Mail can convert Newsgroup messages and/or RSS feeds to emails through the use of free add-ons.

^Selective Download filters can skip/delete messages on POP3 server based on header (sender, recipient, subject, etc) information, this doesn't require to retrieve the full message body from the server.

^Message Dispatcher allows the user to decide which messages should be retrieved, deleted or skipped based on the header information (sender, recipient, subject, etc) displayed to the user.

^ abSSL ports can be chosen in Libremail configuration file but SSL library is not (and will not be) included in Libremail's sources. the website proposes to use Libremail with stunnel software.

^ abcOpera Mail does not support STARTTLS command on special ports, like 995 for pop3 connection

^ abSince version 4.2, The Bat! supports two modes of X.509 certificate handling: Internal Implementation and via Microsoft Crypto API. CRLs and OCSP are only supported in the latter mode during TLS connections.

For all of these clients, the concept of "HTML support" does not mean that they can process the full range of HTML that a web browser can handle. Almost all email readers limit HTML features, either for security reasons, or because of the nature of the interface. CSS and JavaScript can be especially problematic. A number of articles describe these limitations per-email-client; see 1, 2, 3, and 4

^Plain text is the only format to write Emails messages. For emails received both in text and HTML format, the text section is shown by default, but it is possible to watch the HTML section as text, with or without HTML tags

^As libremail dowloads each mail in a separate file, it is possible to sort them in different directories or to delete them according to the content of a header field using a UNIX command.

^Any header field can be tested to delete emails from server. Filtering from sender's address works with domain names and adresses with a variable part. There are also tools to refuse pure HTML emails and emails exceding a chosen size.

^ abcThe Bat! supports two modes of S/MIME: Internal Implementation and via Microsoft Crypto API.[53] CRLs and OCSP are only supported in the latter mode. Internal implementation only supports Aladdin eToken Pro or Rainbow iKey1000[54] tokens and can import certificates (from PKCS#12/PFX format) which were created outside The Bat!. CryptoAPI supports any kind of tokens and smart cards which have a corresponding Cryptographic Service Provider installed.

^ abIt's a frequent problem for people dealing with Cyrillic/Russian in email messages that the message is not encoded in the encoding declared in its headers and thus can't be read. With such a message (with a wrong declaration of the encoding), it well might be the case that it passed through several incorrect recoding stages while it was being sent and delivered; thus it's not possible to correctly render it and read it if one uses the common type of the interface for choosing the encoding (such as the menu in Mozilla Firefox). An example of such a complex case of a wrongly declared encoding: a message was entered through a webform in the windows-1251 encoding, but the web interface incorrectly assumed that it was in latin-1; based on this assumption, it performed the recoding from latin-1 to utf-8. The result of this operation cannot be correctly decoded through the common encoding-selection interface; it can only be decoded through a two-stage recoding: first from utf-8 to latin-1, then from windows-1251 to utf-8 (assuming that one works in a Unicode environment). After it is decoded, it is desirable to store it in the recoded form instead of the original, in order to be able to read it easily afterwards, and to quote it for replies.

^i.Scribe / InScribe supports full integration with GNU Aspell, which is its requirement for spell checking.

^Starts replies with cursor at top, but is configurable regarding whether to include a blank space at the top for replies or not; some interleaved-posting users prefer starting the cursor at the top so they can trim the quotes

^The recoding engine and interface extensions that would solve the described recoding problems have been developed as a patch for Pine; it is to be found in the package pine-4.58L-alt4.src.rpm(ftp) for ALTLinux (under the name pine-4.58L-alt2-0.4.1.diff). Its essential feature is to enable to forcibly recode messages, save them in the recoded form, and quote in replies.

^Pine supports full integration with GNU Aspell or other external speller, which is its requirement for spell checking.

^ abFragmented messages make it possible, for example, to send a large audio message as several partial messages, and still have it appear to the recipient as a simple audio message rather than as an encapsulated message containing an audio message. RFC 2046

^With Entourage 2008, you can use AppleScript and various internal/external scheduling mechanisms to create timed backups of Entourage Data.

^With Entourage 2008 and later versions of 2004, you can use the Spotlight data to search what's in the Entourage database via regular expression in the file system in Terminal or via Spotlight's ...interesting...version of "regular expressions".

^Thunderbird's interface can be user customized via the use of themes (which can reposition and skin controls)

^This is for Mulberry's 'offline browsing' capability, which is turned off by default. In the default configuration no local copy of the mail is created.

^ abcdMulberry is a dedicated IMAP client; If the IMAP server has these abilities, Mulberry can use them.

^ abBecause MH stores each letter in a separate file, it is trivially easy to (externally) search them with grep. This ease is shattered when non-raw encodings are used, such as base64.

^The Bat! Pro support two methods access to program when database is encrypted: password authorization and token authorization; Voyager support only password authorization and encrypted database is default and only available storage method.